Pressure relief type overpressure cause type identification and pressure relief amplitude quantitative evaluation method

Abstract

The invention discloses a pressure relief type overpressure cause type identification and pressure relief amplitude quantitative evaluation method, and relates to the field of oil drilling technology and geophysics, and the method comprises the steps: S1, obtaining data, and carrying out the preprocessing of the data; s2, on the basis of the data in the S1, a formation pressure distribution diagram is constructed, and the position of a pressure relief layer is determined; s3, determining well logging parameters of the pressure relief layer according to the position of the pressure relief layer in the S2; s4, a pressure relief type overpressure identification chart is established based on the pressure relief layer logging parameters in the S3, and the reservoir overpressure cause type of the research position is discriminated; s5, constructing a pressure relief type overpressure quantitative evaluation monitoring model according to the pressure relief type overpressure type in the S4; and S6, evaluating the stratum pressure relief amplitude of the research area based on the pressure relief type overpressure quantitative evaluation monitoring model constructed in the step S5. According to the method, the pressure relief type overpressure type of the earth surface land acquisition layer can be intuitively observed, the reservoir pressure relief amplitude can be quantitatively calculated, and the method has important application value in the fields of resource exploration, oil development, geological engineering and the like.

Description

Technical Field

[0001] The present invention relates to the fields of oil drilling technology and geophysics, and particularly to a method for identifying the cause type of pressure relief type overpressure and quantitatively evaluating the pressure relief amplitude. Background Art

[0002] In the field of geophysics, density curves are usually used to reflect the pore volume size of reservoir rocks, and acoustic velocity and resistivity curves are used to reflect the pore size, shape and connectivity between pores of reservoir rocks. Acoustic velocity and density are important physical properties of underground media. Abnormal formation pressure in the formation can cause changes in acoustic velocity and density. Therefore, acoustic velocity and density crossplots can be used to identify the cause type of pressure relief type abnormal formation pressure. Acoustic velocity is the speed at which sound waves propagate in a medium, and is directly affected by the density and elastic modulus of the medium. Density is the mass per unit volume of the medium. When the formation pressure is abnormal, the pore pressure of underground rocks increases, resulting in an increase in density. At the same time, the elastic modulus of the rocks will also be affected by the pressure, thereby causing changes in acoustic velocity. By measuring the acoustic velocity and density of underground media and plotting them into a crossplot, the change patterns of acoustic velocity and density under different formation pressure types can be observed. For example, normal pressure formations usually have lower acoustic velocity and density, while abnormal pressure formations have higher acoustic velocity and density. Pressure relief formations may show abnormal distributions of acoustic velocity and density.

[0003] The discrimination of the abnormal high pressure formation mechanism is the basis for scientifically selecting the pore pressure calculation method. For example, for abnormal high pressure caused by non-undercompaction mechanism, if the pressure evaluation method under the conventional undercompaction mechanism is directly used without judgment, it may result in a low pressure calculation result and cause very serious drilling accidents. Summary of the Invention

[0004] Aiming at the above existing problems, the present invention aims to provide a method for identifying the cause type of pressure relief type overpressure and quantitatively evaluating the pressure relief amplitude. By analyzing the relationship between the pressure relief type overpressure identification chart and the reservoir abnormal pressure, the abnormal changes in acoustic velocity and density caused by pressure relief type pressure anomalies in the formation can be observed, and then the abnormal high pressure can be identified and the pressure relief amplitude can be quantitatively evaluated.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] A method for identifying the cause type of pressure relief type overpressure and quantitatively evaluating the pressure relief amplitude, characterized by comprising the following steps:

[0007] S1: Obtain the logging parameters and formation pressure data of the target reservoir in the study area, and preprocess the density parameter in the logging parameters;

[0008] S2: Based on the formation pressure data, the well logging and logging parameters without preprocessing, and the preprocessed density parameters in S1, construct a formation pressure distribution map, and combine it with the well logging response pattern map to determine the layer position of the pressure relief layer;

[0009] S3: Determine the well logging and logging parameters of the pressure relief layer according to the layer position of the pressure relief layer determined in S2;

[0010] S4: Establish an overpressure identification chart for pressure relief type based on the well logging and logging parameters of the pressure relief layer determined in S3, and identify the overpressure origin type of the target reservoir in the study area according to the overpressure identification chart for pressure relief type;

[0011] S5: Construct a quantitative evaluation and monitoring model for overpressure of pressure relief type according to the overpressure origin type in S4;

[0012] S6: Evaluate the pressure relief amplitude of the target reservoir in the study area based on the quantitative evaluation and monitoring model for overpressure of pressure relief type constructed in S5.

[0013] Furthermore, in S1, the well logging and logging parameters include: acoustic travel time, density, resistivity, Dc index;

[0014] The formation pressure data includes: formation pore pressure, overlying rock pressure.

[0015] Furthermore, in S1, the preprocessing of the well logging and logging parameters is specifically the preprocessing of density, including the following steps:

[0016] S1.1: Obtain formation bulk density data through density logging;

[0017] S1.2: Obtain the true formation bulk density data by correcting the formation bulk density data in S1.1; the formation bulk density data correction formula is:

[0018] ρ e =ρ fm (1 - V sh ) + ρ sh V sh (1.1)

[0019] In the formula, ρ e is the density value of the current sampling point; ρ fm is the pure rock density value; ρ sh is the shale density value; V sh is the shale content;

[0020] S1.3: Based on the true formation bulk density data obtained in S1.2, correct the influence of water-based drilling fluid soaking on the reservoir density to obtain the preprocessed density, and the correction formula is as follows:

[0021] ρ c =[(a + bρb ) - ρ b V sh +ρ b (1.2)

[0022] In the formula, ρ c is the corrected density value; ρ b is the density log value; a and b are model coefficients, and ρb is the ρe in S1.2.

[0023] Furthermore, the S2 includes the following sub - steps:

[0024] S2.1: Based on the pre - processed logging and well - logging parameters and formation pressure data in S1, draw the relationship curves of acoustic velocity and formation pressure coefficient varying with formation depth, and obtain the formation pressure distribution map of the study area;

[0025] S2.2: Based on the formation pressure distribution map established in S2.1 and combined with the logging response pattern map, determine the layer positions of pressure - releasing layers.

[0026] Furthermore, the S5 includes the following sub - steps:

[0027] S5.1: Based on the pressure - releasing type of overpressure in S4, draw the relationship curve between acoustic velocity and effective stress, and obtain that the relationship curve between acoustic velocity and effective stress conforms to the re - loading equation;

[0028] S5.2: Based on the re - loading equation in S5.1, establish a quantitative evaluation and monitoring model for pressure - releasing type of overpressure. The formula is as follows:

[0029]

[0030] In the formula, PP is the formation pressure of the pressure - releasing layer; OBG is the overburden rock pressure; PPN is the normal hydrostatic pressure; DTN is the acoustic travel time of the normal trend line corresponding to the calculation point; DT O is the acoustic travel time of the calculation point; x is the Eaton index; α is the pressure - releasing coefficient.

[0031] Furthermore, the S6 includes the following sub - steps:

[0032] S6.1: Based on the quantitative evaluation and monitoring model for pressure - releasing type of overpressure obtained in S5, substitute the formation pressure data of the reservoir, the un - pre - processed logging and well - logging parameters, and the pre - processed density parameters, and calculate the formation pressure after the reservoir pressure - releasing;

[0033] S6.2: Subtract the formation pressure after the reservoir pressure - releasing from the original formation pressure, and the pressure - releasing amplitude of the target reservoir in the study area can be obtained.

[0034] The beneficial effects of the present invention are: Compared with the prior art, the improvements of the present invention are:

[0035] Based on the traditional chart for identifying the causes of overpressure in reservoirs and combined with the law of reservoir pressure relief, this application draws a chart for identifying overpressure of the pressure relief type. By analyzing the relationship between the chart for identifying overpressure of the pressure relief type and the abnormal reservoir pressure, abnormal changes in acoustic velocity and density caused by pressure anomalies of the pressure relief type in the formation can be observed. Rocks under high pressure usually undergo compaction, resulting in an increase in acoustic velocity and density. However, pressure relief induces an increase in effective stress, leading to a significant increase in acoustic velocity, while the density and Dc index remain basically unchanged.

[0036] The chart for identifying overpressure of the pressure relief type is a further supplement to the traditional chart, improving the problem that the traditional chart lacks the identification of the causes of overpressure of the pressure relief type. It provides an intuitive and quantitative method for distinguishing the types of causes of abnormal formation pressure, which helps to identify the causes of abnormal pressure of the pressure relief type in the formation. This has important application value in the fields of resource exploration, oil development, geological engineering, etc. Description of the Drawings

[0037] Figure 1 It is a curve graph showing the variation of acoustic velocity and density with depth according to the present invention.

[0038] Figure 2 It is a curve graph showing the variation of acoustic velocity and density with depth after supplementation, screening, and processing according to the present invention.

[0039] Figure 3 It is a formation pressure distribution map according to the present invention.

[0040] Figure 4 It is a logging mode response map of the pressure relief layer according to the present invention.

[0041] Figure 5 It is a chart for identifying the causes of abnormal formation pressure based on the acoustic velocity-density crossplot of Well X according to the present invention.

[0042] Figure 6 It is a chart for identifying the causes of abnormal formation pressure based on the acoustic velocity-Dc index crossplot of Well Y according to the present invention.

[0043] Figure 7 It is a relationship curve between acoustic velocity and effective stress of the overpressure type of the pressure relief type according to the present invention. Detailed Embodiments

[0044] In order to enable ordinary technicians in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be further described below with reference to the drawings and embodiments.

[0045] Embodiment 1

[0046] Please refer to Figures 1-7, A method for identifying the causes of overpressure of the pressure-relief type and quantitatively evaluating the pressure-relief amplitude, comprising the following steps:

[0047] S1: Obtain the logging parameters and formation pressure data of the target reservoir in the study area, and preprocess the logging parameters;

[0048] Specifically, the logging parameters and formation pressure data include: acoustic travel time, density, resistivity, Dc index, formation pore pressure, and overburden pressure.

[0049] Since acoustic velocity and density logging data are easier to obtain and have higher data accuracy compared to porosity and resistivity, in addition to using acoustic velocity, resistivity, and density logging curves to compare and judge normal compaction and undercompaction (loading), non-undercompaction such as fluid expansion (unloading), it is also possible to use an acoustic velocity-density crossplot to identify the cause types of pressure-relief type abnormal high pressure. The method of using an acoustic velocity and density crossplot to identify the cause of abnormal formation pressure can be applied in fields such as oil exploration and geological disaster prediction, which helps to better understand the changes in underground media.

[0050] Therefore, in this embodiment, it is preferred to use acoustic velocity, density, or Dc index parameters to identify the pressure-relief type overpressure.

[0051] In S1, the acoustic velocity is the propagation velocity of sound waves in a medium, where the propagation velocity in air is 340 m / s and the propagation velocity is different in different media. The acoustic velocity of the mudstone formation can be obtained by using the logging acoustic travel time and cuttings logging stratification data.

[0052] In S1, the formation bulk density change with depth is obtained through density logging. Before obtaining as accurate formation bulk density data as possible, a series of processing is required for the original density data, including density logging data screening, density logging data correction, density curve stratification reading, and manually removing some abnormal points;

[0053] Specifically, in S1, the following method is used to estimate the density value of the current sampling point:

[0054] S1.1: Obtain the formation bulk density data through density logging;

[0055] S1.2: Correct the formation bulk density data in S1.1 to obtain the true formation bulk density data; the formation bulk density data correction formula is:

[0056] ρ e =ρ fm (1 - V sh ) + ρ sh V sh (1.1)

[0057] In the formula, ρe is the density value of the current sampling point; ρ fm is the density value of pure rock; ρ sh is the density value of mudstone; V sh is the shale content;

[0058] S1.3: Based on the true formation bulk density data obtained in S1.2, correct the influence of water-based drilling fluid immersion on the reservoir density. The formula is as follows:

[0059] ρ c = [(a + bρ b ) - ρ b V sh + ρ b (1.2)

[0060] In the formula, ρ c is the corrected density value; ρ b is the density log value; a and b are model coefficients. ρb in S1.3 is ρe in S1.2.

[0061] S2: Based on the preprocessed logging and well testing parameters and formation pressure data in S1, construct a formation pressure distribution map, and combine it with the logging response pattern map to determine the layer position of the pressure relief layer;

[0062] In S2, draw a formation pressure distribution map according to the reservoir logging and well testing parameters and formation pressure parameters as shown in Figure 3 and combine it with the logging response pattern map as shown in Figure 4 to determine that the layer position of the pressure relief layer is the pink marked area in Figure 3 .

[0063] Specifically, S2 includes:

[0064] S2.1: Based on the logging and well testing parameters obtained in S1, draw the relationship curves of acoustic velocity and formation pressure coefficient changing with formation depth to obtain the formation pressure distribution map of the study area;

[0065] S2.2: Based on the formation pressure distribution map established in S2.1, combine it with the logging response pattern map to determine the layer position of the pressure relief layer;

[0066] S3: According to the layer position of the pressure relief layer determined in S2, determine the logging and well testing parameters of the pressure relief layer;

[0067] Specifically, according to the layer position of the pressure relief layer determined in S2, screen out the logging and well testing parameters corresponding to the layer position of the pressure relief layer from the preprocessed logging and well testing parameters in S1. Include acoustic velocity and density parameters.

[0068] S4: Based on the logging and well testing parameters of the pressure relief layer determined in S3, establish a pressure relief type overpressure identification chart, and identify the overpressure origin type of the reservoir in the study layer according to the pressure relief type overpressure identification chart;

[0069] Specifically, the process of establishing the pressure-relief type overpressure identification chart involved in S4: It is obtained by combining the pressure-relief type overpressure mechanism on the basis of the traditional overpressure origin discrimination chart of reservoirs. And after the establishment of the pressure-relief type overpressure identification chart, its discrimination method is: When the reservoir is pressure-relieved, as the burial depth increases, the effective stress of the reservoir increases, the acoustic velocity increases, and the density and Dc index remain basically unchanged. The cause type of the abnormal formation pressure at this time is the pressure-relief type overpressure.

[0070] It should be noted that in S4, by importing the acoustic velocity and density into the excel software for processing and plotting to generate the overpressure origin identification chart, it can be judged whether it is the cause of fluid pressure-relief type overpressure.

[0071] The coordinate system used for the chart is the Cartesian rectangular coordinate system, where the abscissa of the coordinate system is the density and the ordinate of the coordinate system is the acoustic velocity.

[0072] The relationship curve of acoustic velocity-effective stress and density-vertical effective stress can be additionally plotted to enhance the accuracy of abnormal pressure identification.

[0073] And in S4, pressure relief leads to a decrease in formation pore pressure, an increase in effective stress, compaction of pore throats, an increase in acoustic velocity, and the density and Dc values remain basically unchanged. In the acoustic velocity-density (or Dc index) cross plot, a typical characteristic of the pressure-relief type abnormal formation pressure is that after fluid pressure relief, the density remains basically unchanged, but the acoustic velocity changes significantly. Therefore, the cause type of the abnormal formation pressure can be identified by observing the relative change trend of the acoustic velocity and density in the acoustic velocity-density cross plot.

[0074] S5: Based on the pressure-relief type overpressure type in S4, plot the relationship curve between its acoustic velocity and effective stress. As Figure 7 shown, it is found that its acoustic time difference increases significantly with the increase of effective stress, which conforms to the reloading equation. Therefore, based on the reloading equation, that is, the Eaton method, a pressure-relief type overpressure quantitative evaluation and monitoring model based on the Eaton method is established.

[0075] Specifically, the formula of the Eaton method is:

[0076]

[0077] Specifically, the pressure-relief type overpressure quantitative evaluation and monitoring model based on the Eaton method is:

[0078]

[0079] In the formula, PP is the formation pressure of the pressure-relief layer; OBG is the overburden pressure; PPN is the normal hydrostatic pressure; DTN is the acoustic time difference of the normal trend line corresponding to the calculation point; DTO To calculate the acoustic travel time of a point; x is the Eaton index; α is the pressure relief coefficient.

[0080] It should be noted that x and α can be obtained by fitting according to the actual logging data of the formation.

[0081] S6: Evaluate the formation pressure relief amplitude of the study area based on the pressure relief type overpressure quantitative evaluation and monitoring model constructed in S5.

[0082] Specifically, S6 includes:

[0083] S6.1: Based on the pressure relief type overpressure quantitative evaluation and monitoring model obtained in S5, substitute the formation pressure data of the reservoir, the unprocessed logging parameters, and the preprocessed density parameters to calculate the formation pressure after the reservoir is pressure relieved.

[0084] S6.2: The original formation pressure minus the formation pressure after the reservoir is pressure relieved is the pressure relief amplitude of the reservoir in this study area.

[0085] As Figure 5 shown, when the effective stress increases, the acoustic wave increases significantly, but the density remains basically unchanged. At this time, the cause type of abnormal formation pressure in the study section of Well X is pressure relief type overpressure.

[0086] Example 2

[0087] In this example, the analysis steps and methods for identifying the cause of formation pressure are the same as those in Example 1, except that the abscissa used in the cross plot is different. As Figure 6 shown, in this example, the Dc index is used as the abscissa and the acoustic wave velocity is used as the ordinate. When the effective stress increases, the acoustic wave velocity increases significantly, but the Dc index remains basically unchanged. Therefore, the cause type of abnormal formation pressure in the study section of Well Y is pressure relief type overpressure.

[0088] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for identifying the type of overpressure cause of a pressure relief type and quantitatively evaluating the pressure relief amplitude, characterized in that, It includes the following steps: S1: Obtain the logging parameters and formation pressure data of the target reservoir in the study area, and preprocess the density parameter in the logging parameters; S2: Based on the formation pressure data in S1, the un-preprocessed logging parameters, and the preprocessed density parameter, construct a formation pressure distribution map, and combine it with the logging response pattern map to determine the layer position of the pressure-relief layer; S3: According to the layer position of the pressure-relief layer determined in S2, determine the logging parameters of the pressure-relief layer; S4: Establish a pressure-relief type overpressure identification chart based on the logging parameters of the pressure-relief layer determined in S3, and identify the overpressure formation type of the target reservoir in the study area according to the pressure-relief type overpressure identification chart; S5: Construct a pressure-relief type overpressure quantitative evaluation and monitoring model according to the overpressure formation type in S4; S6: Evaluate the pressure-relief amplitude of the target reservoir in the study area based on the pressure-relief type overpressure quantitative evaluation and monitoring model constructed in S5.

2. The method for identifying the type of overpressure cause and quantitatively evaluating the pressure relief amplitude of a pressure relief type according to claim 1, wherein: In S1, the logging parameters include: acoustic travel time, density, resistivity, Dc index; The formation pressure data includes: formation pore pressure, overlying rock pressure.

3. The method for identifying the type of overpressure cause and quantitatively evaluating the pressure relief amplitude of a pressure relief type according to claim 2, characterized in that In S1, the preprocessing of the logging parameters specifically refers to the preprocessing of density, including the following steps: S1.1: Obtain the formation bulk density data through density logging; S1.2: Correct the formation bulk density data in S1.1 to obtain the true formation bulk density data; the formation bulk density data correction formula is: ρ e = ρ fm (1 - V sh ) + ρ sh V sh (1.1) where ρ e is the density value of the current sampling point; ρ fm is the pure rock density value; ρ sh is the shale density value; V sh is the shale content; S1.3: Based on the true formation bulk density data obtained in S1.2, correct the influence of water-based drilling fluid immersion on the reservoir density to obtain the preprocessed density, and the correction formula is as follows: ρ c = [(a + bρ b ) - ρ b V sh + ρ b (1.2) where ρ c is the corrected density value; ρ b is the density log value; a and b are model coefficients, The said ρ b is the ρ in S1.2 e .

4. A method for identifying the type of overpressure cause of a pressure relief type and quantitatively evaluating the pressure relief amplitude according to claim 1, characterized in that The said S2 includes the following sub-steps: S2.1: Based on the preprocessed logging parameters and formation pressure data in S1, draw the relationship curves of acoustic velocity and formation pressure coefficient changing with formation depth to obtain the formation pressure distribution map of the study area; S2.2: Based on the formation pressure distribution map established in S2.1, combine it with the logging response pattern map to determine the layer position of the pressure-relief layer.

5. A method for identifying the type of overpressure cause of a pressure relief type and quantitatively evaluating the pressure relief amplitude according to claim 1, characterized in that, The said S5 includes the following sub-steps: S5.1: Based on the pressure-relief type overpressure type in S4, draw the relationship curve between acoustic velocity and effective stress to obtain that the relationship curve between acoustic velocity and effective stress conforms to the reloading equation; S5.2: Based on the reloading equation in S5.1, establish a pressure-relief type overpressure quantitative evaluation and monitoring model, and the formula is as follows: Wherein, PP is the formation pressure of the pressure relief layer; OBG is the overlying rock pressure; PPN is the normal hydrostatic pressure; DTN is the acoustic time difference of the normal trend line corresponding to the calculation point; DT O is the acoustic time difference of the calculation point; x is the Eaton index; α is the pressure relief coefficient.

6. The method for identifying the type of overpressure cause and quantitatively evaluating the pressure relief amplitude of a pressure relief type as claimed in claim 1, wherein The said S6 includes the following sub-steps: S6.1: Based on the pressure-relief type overpressure quantitative evaluation and monitoring model obtained in S5, substitute the formation pressure data, un-preprocessed logging parameters, and preprocessed density parameters of the reservoir to calculate the formation pressure after reservoir pressure relief; S6.2: Subtract the formation pressure after reservoir pressure relief from the original formation pressure to obtain the pressure-relief amplitude of the target reservoir in the study area.

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